1. Field of the Invention
The invention generally relates to power driven conveyors. More specifically, the invention relates to a conveyor section of an endless conveyor and to the support, guide, or hold-down means for the carrier belt, especially to a means slidably supporting the belt.
2. Description of the Prior Art
Conveyor belts adapted to move along a curved path are disclosed in U.S. Pat. No. 2,701,050 to Steinborn, U.S. Pat. No. 2,836,283 to Horth, U.S. Pat. No. 3,169,631 to Knappe, and U.S. Pat. No. 4,144,965 to Alldredge et al. The conveyors of those patents, which are manufactured under the Serpentix trademark, are supported on laterally spaced multiple rollers at various points along the length of the conveyor belt and follow a pair of laterally spaced apart, channel shaped steel rails that define the conveyor path. A central chain pulls the conveyor on the rollers. Since the load is carried on rollers that are widely displaced from the single chain on the centerline, this type of conveyor does not present lateral stability problems, but there may be chording problems in horizontal and helical turns.
In addition, the above noted patent to Alldredge et al. discloses flexible rail sections that employ a series of short steel rail segments that are linked to each other by mating tongues in order to provide a continuous pathway over a curved rail section. These multi-rail, roller type conveyors with convoluted belt are well suited for heavy duty applications and provide a valuable industrial advantage through their ability to follow a curved path. However, their construction through helical and other curved sections can require considerable technical skill and precision to ensure that the track sections are properly aligned and smooth.
A further U.S. Pat. No. 4,422,544 to Alldredge discloses a centerline pull chain conveyor in which the chain carries rollers that engage a centerline, cruciform channel. A pair of mirror-image steel side sections define the channel and are bolted to a common steel web below the channel. This type of conveyor is easier to construct than the previously mentioned roller type, since only one rail or channel is necessary to define each curve. Also, this type of conveyor operates with low friction and can negotiate a large degree of curvature in its pathway.
Another type of Serpentix conveyor adapted to follow a curved path and employing the same style of belt is disclosed in U.S. Pat. No. 4,438,842 to Alldredge et al. This type of conveyor is a slide or drag conveyor, in which a convoluted belt that carries the material being conveyed is above a single chain. The chain both pulls the load and prevents the loaded belt from tipping to one side sufficiently to spill the load to the side. In the preferred embodiment, the belt rides on a single-bar supporting link of a conveyor chain that employs single-bar links alternating with double-bar links, all of which slide through a single, centerline, guiding channel. The chain, rather than rollers, bears the weight of the load and prevents the load from tipping. This single-bar link is free to twist and tilt sideways until it reaches the alternating double-bar links. As the double-bar links begin to restrain the twisting, the stabilizing lever arm is transferred from the outer lower edge of the single link to the outer lower edge of the double link, which provides a longer lever arm because the double-bar links are wider than the single-bar links. In some applications the single-bar links are limited in the amount of twisting by contacting the sides of the lip on the slide channel. Where tilting of the belt must be kept to a minimum, small rollers can be installed inside or outside the slide channel to provide a longer lever arm.
The centerline channel is considerably easier to construct than the rails of the roller type conveyors, and this slide channel conveyor also has the ability to follow a curved path. However, the load bearing capacity of a slide conveyor generally will be lower than that of a conveyor riding on rollers, and the total degree of curvature may be more limited. Nevertheless, this type of conveyor is well suited to many applications and has advantages in cost and ease of fabrication.
In another commercially available design that is similar in structure to the patented centerline slide conveyor, the conveyor belt is connected to a plastic attachment, which is bolted to the single-bar link of the chain. Lateral extensions or runners on the plastic attachment prevent the fastening bolt from reaching and cutting the plastic sides of the slide channel. The resistance to tilting is provided on part by the feature that the single-bar link reaches and bears upon the double-bar link; and twisting of the double-bar link is limited because of the snug fit of the double-bar link in the slide channel.
Generally speaking, in a slide channel conveyor of the types described, the basic design problem is stabilization. The problem of supporting a relatively wide belt above a relatively narrower central carrier chain requires that there be horizontal axis stabilization. Thus, it is desirable to provide improved and less costly techniques of preventing the conveyor belt from tipping excessively.
To achieve the foregoing and other objects and in accordance with the purpose of the present invention, as embodied and broadly described herein, the conveyor channel and method of manufacture of this invention may comprise the following.